1. FIELD OF THE INVENTION
The present invention relates to a method of forming a paper web having a low tensile ratio. More particularly, the present invention relates to a method of forming a paper web in which a gradual dewatering of the ejected stock is accomplished, thereby inhibiting removal of fines from the ejected stock and minimizing the tensile ratio of the resultant web.
2. INFORMATION DISCLOSURE STATEMENT
During the manufacture of a web of paper, many factors interact in order to impart particular characteristics to the resultant web.
For example, when stock is ejected from a headbox onto a moving fourdrinier wire, the ratio of the velocity of the ejected stock to the velocity of the moving fourdrinier wire has an affect on the resultant web.
For certain paper grades, particularly for fine paper, the tensile strength of a web in a machine direction should be as close as possible to the tensile strength of the web in the cross-machine direction.
In the papermaking art, such ratio of the aforementioned tensile strength in the machine direction to the cross-machine direction is known as the "tensile ratio".
Particularly during the manufacture of envelopes and the like, it is desirable that the tensile ratio be as near as possible to unity, so that during the paper converting operation the sheet of paper responds equally regardless of the direction in which the sheet is folded.
The Horizontal Bel Baie forming machine taught in U.S. patent application 07/127,525, now U.S. Pat. No. 4,894,120, assigned to Beloit Corporation characteristically has a high drainage capacity and includes the advantage of fines retention within the ejected stock. Nevertheless, the Horizontal Bel Baie typically does not form a web having a tensile ratio less than two, regardless of the aforementioned jet-to-wire ratio. Horizontal Bel Baie is a trademark of Beloit Corporation.
The present invention overcomes the aforementioned problem of manufacturing a web having a relatively low tensile ratio by incorporating the features of the Horizontal Bel Baie and a curved inverted vacuum box of a twin wire Bel Bond machine, together with an initial single wire dewatering zone.
Therefore, it is a primary object of the present invention to provide a method of forming a paper web having a low tensile ratio, the method providing a significant and nonobvious contribution to the art of papermaking.
Another object of the present invention is the provision of a method of making a paper web having a low tensile ratio while maintaining fines retention.
Other objects and advantages of the present invention will be apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.